Transformer windings are typically formed by winding an electrical conductor, such as copper or aluminum wire, on a continuous basis. The electrical conductor can be wound around a mandrel, or a directly onto a winding leg of the transformer. The electrical conductor is wound into a plurality of turns in side by side relationship to form a first layer of turns. A first layer of insulating material is subsequently placed around the first layer of turns. The electrical conductor is wound into a second plurality of turns over the first layer of insulating material, thereby forming a second layer of turns.
A second layer of insulating material is subsequently placed over the second layer of turns. The electrical conductor is then wound into a third plurality of turns over the second layer of insulation, thereby forming a third layer or turns. The above procedure can be repeated until a predetermined number of turn layers have been formed.
Heat-curable epoxy diamond pattern coated kraft paper (commonly referred to as “DPP paper”) is commonly used as the insulating material in transformer windings. A transformer winding comprising DPP paper is typically heated after being wound in the above-described manner. The heating is necessary to melt and cure the epoxy adhesive on the DPP paper and thereby bond the DPP paper to the adjacent layer or layers of the electrical conductor. The transformer winding can be heated by placing the transformer winding in a hot-air convection oven (or other suitable heating device) for a predetermined period of time.
Transferring the transformer winding to a hot-air convection, and the subsequent heating process can increase the cycle time associated with the manufacture of the transformer winding. Moreover, the energy requirements of the hot-air convection oven can increase the overall manufacturing cost of the transformer winding. Also, it can be difficult to achieve uniform heating (and curing of the adhesive) throughout the transformer winding using a hot-air convection oven. Hence, adequate bonding between specific layers of the insulating material and the electrical conductor can be difficult to obtain (particularly between the innermost layers of the insulating material and the electrical conductor).